The Pearl Harbor destroyer USS Preble on Monday conducted its third “freedom of navigation” operation in the South China Sea since February in what so far has been four such Navy challenges to China’s claims this year.

The pace is far ahead of last year’s operations — five — with the Defense Department expected to announce details of a new Indo-Pacific strategy at the end of the month.

The Navy also took the unusual step of revealing that the Pearl Harbor-based submarine USS Hawaii was in the Indian Ocean last week as part of an exercise involving a French aircraft carrier and its escort ships.

It all adds up to an increased Navy and allied presence for Hawaii and others ships in the increasingly volatile region as part of an evolving “free and open Indo-Pacific” campaign aimed at China and amid growing concerns over Iran.

It also raises the question of whether U.S. warships will be sailing into more trouble with China in the South China Sea.

Carl Schuster, a retired Navy captain, former director of operations at U.S. Pacific Command’s Joint Intelligence Center and adjunct professor at Hawaii Pacific University, said the United States is headed for a new strategy with freedom of navigation operations in the South China Sea codified as part of regular and ongoing behavior.

“I think what we’re doing now is we’re setting up the precedent for (the Navy) to just say, ‘We’re going to do it no matter what you (China) say,’” Schuster said. “The dilemma that puts the Chinese in is, do they respond in an aggressive way that … carries with it a lot of risk? Or, do they just live with it? I’m not sure which they’ll do. I do know it will affect their calculations.”

In September, in what to date has been an anomaly, a Chinese destroyer overtook the USS Decatur as it was conducting a freedom of navigation operation near Gaven Reef in the Spratly Islands and closed within a dangerous 45 yards of the U.S. destroyer.

The Chinese ship issued a radio warning stating, “If you don’t change course, (you) will suffer consequences.”

In Monday’s operation the Preble sailed within 12 nautical miles of Scarborough Shoal — a feature controlled by China but also claimed by Taiwan and the Philippines — “in order to challenge excessive maritime claims and preserve access to the waterways as governed by international law,” said the Navy’s 7th Fleet.

“U.S. Forces operate in the Indo-Pacific region on a daily basis, including in the South China Sea,” said Cmdr. Clay Doss. “All operations are designed in accordance with international law and demonstrate that the United States will fly, sail and operate wherever international law allows.”

China Foreign Ministry spokesman Lu Kang said the Preble “trespassed into the adjacent waters” of the shoal it calls Huangyan Dao without permission from the Chinese government.

“The Chinese Navy identified and verified the U.S. warship according to law, and warned it off. I have to stress again that the trespass of U.S. warship is a violation of China’s sovereignty,” Lu said.

The United States does not recognize the shoal as China’s territory. An estimated $3.4 trillion worth of international shipping passes through the South China Sea each year, and the United States wants free and open access.

The Congressional Research Service said in a January report that a key question for Congress is whether the Trump administration “has an appropriate strategy — and an appropriate amount of resources for implementing that strategy” to counter China’s “gray zone” operations short of war as it consolidates power in the South China Sea.

Schuster said the United States has become less predictable about freedom of navigation operations.

In February the Preble and the USS Spruance, out of San Diego, sailed near the Spratly Islands. More recently, on May 6, the Preble and the USS Chung-Hoon, also out of Hawaii, operated near Gaven and Johnson reefs.

The announced presence of the Virginia-class submarine USS Hawaii in the Indian Ocean, meanwhile, is a message to both China and Iran, Schuster said.

“A submarine in today’s world carries cruise missiles — which obviously would be a concern to Iran,” he said. If Iran does something provocative, it faces the potential of retaliation.

China has not been able to establish a major naval presence in the Indian Ocean — the transit route for over 50% of its trade, Schuster said.

The USS Hawaii’s presence may be largely directed at Iran, “but it’s something that China can’t ignore as well,” he said. “It sends a signal that we have a greater capacity for near global deployments while you can only establish a minor global presence.”

NAVIGATION TIMELINE

2019 freedom of navigation operations take an unpredictable turn in the South China Sea

Jan. 7

The USS McCampbell, based in Japan, sails near the Paracel Islands.

Feb. 11

The USS Preble out of Hawaii and USS Spruance, from San Diego, operate near the Spratly Islands.

May 6

The USS Preble and USS Chung-Hoon, also out of Hawaii, sail near Gaven and Johnson reefs in the Spratly Islands.

May 20

The USS Preble sails near Scarborough Shoal west of Luzon in the Philippines.

Source: U.S. Navy